By Washington Castilhos
Heitor Cantarella received the International Fertilizer Association’s (IFA) Norman Borlaug Award on World Fertilizer Day, on 13 October — the date German chemist Fritz Haber discovered the synthesis of ammonia in 1908.
Cantarella’s work enables a 95 per cent reduction in emissions of nitrous oxide associated with cane cultivation.
“If we do not control the emissions associated with the production of ethanol, we can lose the benefits of replacing fossil fuels”
Sugarcane is used to produce bioethanol and therefore already contributes to a reduction in carbon dioxide emissions from the burning of fossil fuels. But it releases nitrous oxide which, pound for pound, causes a greenhouse effect approximately 300 times greater than carbon dioxide.
The fertilizers used in agriculture play a significant role in reducing the release of nitrous oxide. Cantarella created a method where urease inhibitors are used during the cultivation of cane to prevent the transformation of urea — the most used fertilizer in Brazilian agriculture — into carbon dioxide. Nitrification inhibitors are also used to block the transformation of ammonia into nitrate.
This is an important step in reducing nitrous oxide emissions, because bacteria in the soil convert nitrate to nitrous oxide and other gases. The researchers calculated a reduction rate of 85-95 per cent for soils with urea and inhibitors, compared with soil with urea or soil without fertilisers.
Brazil is the greatest sugarcane producer in the world and the main exporter of ethanol, which also powers 40 per cent of vehicles in the country.
But “if we do not control the emissions associated with the production of ethanol, we can lose the benefits of replacing fossil fuels,” said Cantarella, director of the Center for Research and Development of Soils and Environmental Resources at the Agronomic Institute of Campinas, in an interview with SciDev.Net. “The role of the use of fertilisers is important to adopt mitigating practices.”
As a signatory to the Paris Agreement on climate change, Brazil must reduce emissions by 43 per cent by 2030. Making sugarcane cultivation sustainable can contribute to this.
In order to fulfill these international commitments, the Brazilian government is currently discussing the Renovabio, a biofuels regulation policy that sets emissions reduction targets.
“The rationalisation of the use of fertilizers puts the production of cane, and consequently ethanol, on a path towards becoming a more sustainable commodity, increasing its value as a replacement for fossil fuels,” says physicist Newton La Scala Junior, from Paulista State University in Sao Paulo.
However, cane cultivation faces challenges in addition to the need for judicious use of fertilizers. One example is the burning of straw residues during harvest, which is responsible for carbon dioxide emissions and respiratory problems due to inhalation of smoke and soot.
Alternatives to the burning of these residues are being studied. La Scala and other researchers are also investigating the benefits of leaving straw lying above ground, to help decrease erosion and provide soil nutrients.